The present application is based on and claims priority from Japanese Patent Application 2000-186277 filed Jun. 21, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotary electric machine and, particularly, a stator arrangement of an ac generator.
2. Description of the Related Art
Recently, compact, powerful and highly efficient vehicle rotary electric machines such as AC generators have been manufactured to meet demand for reduction in idling speed of engines in view of the environmental protection, in weight of vehicles in view of fuel consumption and in the space of engine compartments in view of more comfortable passenger compartments. It is also necessary to provide rotary electric machines that are resistant to environmental hazard such as car-washing shampoo, salt water or other foreign substances, which may get in engine compartment.
In order to provide a compact, powerful and highly efficient AC generator, a cooling fan is fixed to an end of magnetic poles of the rotor thereof. JP-B2-4-24939 discloses an AC generator in which coil ends of each phase coil of a stator winding is made flat to form gaps so that cooling air can flow through the gaps. U.S. Pat. No. 6,049,154 or the corresponding Japanese Patent Application, JP-A-11-299153, discloses a step of shaping a stator winding, in which coil ends are shaped to prevent the coil ends from interfering with each other to eliminate insulation failure. In this structure, each wire extended from a slot is bent inwardly at the middle thereof and inserted into another slot that is spaced apart at a prescribed number of slots. Therefore, a plurality of wires are lined up at the middle bent portion in a circumferential direction.
JP-A-8-275442 discloses an AC generator in which rubber or other thermoplastic resin mixed with silica is filled between the outer periphery of coil ends and a frame so that heat of the stator winding can be transmitted to the frame.
In the AC generator disclosed in JP-B2-4-24939, coil ends overlap each other in the circumferential direction of the AC generator. Therefore, it is difficult to form cooling air passages in the coil ends.
In the AC generator disclosed in U.S. Pat. No. 6,049,154 (or JP-A-11-299153), large spaces are formed at the middle of each bundle of coil ends. However, no space is formed at the remainder of the bundle of the coil ends, and, therefore, the cooling air does not cool the coil ends effectively. If some spaces are formed in the remainder of the bundle of the coil ends, the bundle becomes bulky and may contact the frame. This may cause insulation failure.
In the AC generator disclosed in JP-A-8-275442, the thermoplastic resin may be damaged by salt water, washing shampoo or other foreign substances, thereby causing insulation failure.
Therefore, a main object of the invention is to provide a compact, powerful and highly efficient vehicle rotary electric machine that has an improved cooling arrangement.
A vehicle AC generator according to a feature of the invention includes a rotor having a plurality of claw-shaped pole pieces forming a cooling fan, a cooling fan fixed to an end of the rotor, a stator core which has a plurality of slots and a stator winding and a frame. A coil-end-gap is formed along an axial end of the stator core between outside portions of the stator winding extending from each pair of adjacent slots, and a wall member is disposed between the frame and the coil ends of the stator winding.
Because the rotor having a plurality of claw-shaped pole pieces that function as a fan, cooling air is driven toward the coil-end gaps. Then, the cooling air is guided by the wall member to flow along the whole outer surface of the coil ends. As a result, the coil-ends are effectively cooled.